Grade 7 General Science Practice Flashcards

Comprehensive practice flashcards covering basic concepts of science, matter, chemical reactions, cell biology, kingdoms of life, Earth systems, motion, force, and energy resources from Grade 7 General Science.

What is the definition of science according to its Latin origin?

Science comes from the Latin word 'Scientia', which means 'Knowledge'. It is a systematic method of gaining knowledge about the physical and natural world and the social aspect of human society based on observation and evidence.

How does indigenous science differ from conventional science?

Indigenous science incorporates local people's empirical knowledge and cultural understandings of their natural environment, whereas conventional science relies on established laws derived from the systematic application of the scientific method (commonly recognized as Western science).

Which major scientific discovery was made by Dr. Aklilu Lemma in 1964?

He discovered that berries from the endod plant act as a potent, inexpensive, and safe natural molluscicide to prevent the spread of the parasitic worm causing schistosomiasis (snail fever or bilharzia).

What are the significant achievements of Prof. Yalemtsehay Mekonnen?

Born in Asela on May 30, 1955, she worked on human physiology, the impact of pesticides on human health, and medicinal plants against human and animal diseases, and became the first female professor of Addis Ababa University.

What hazard does this laboratory warning sign indicate?

Biological Hazard (Biohazard).

What is the proper laboratory procedure for diluting concentrated acid solutions?

Always add acid into water (remembering the Amharic mnemonic 'AW! Not WA!', where A = acid and W = water). Never add water to concentrated acid.

What is the scientific definition of matter?

Matter is anything that has mass and occupies space. Forms of energy such as light, heat, and sound are not matter.

What are the six main postulates of the particle theory of matter?

1. All matter is made up of tiny particles.
2. The particles move continuously.
3. The particles have spaces between them.
4. Adding heat makes particles move faster.
5. There are forces between particles.
6. Particles of one substance differ from particles of another.

What is diffusion, and how does its rate compare across the three states of matter?

Diffusion is the net movement of particles from an area of high concentration to an area of low concentration. It is fastest in gases, slower in liquids, and extremely slow in solids.

What term describes the phase change directly from a solid to a gas, and what are common examples?

Sublimation. Common examples include iodine, ammonium chloride, and solid carbon dioxide (dry ice).

What phase change corresponds to the direct transition from a gas to a solid?

Deposition.

How do intensive physical properties differ from extensive physical properties?

Extensive properties depend on the amount of sample present (e.g., mass, volume, length), whereas intensive properties do not depend on sample size and help distinguish substances (e.g., density, color, melting point, boiling point).

What are the defining physical properties of metallic elements?

Metals are shiny (lustrous), malleable (can be hammered into sheets), ductile (can be drawn into wires), good conductors of heat and electricity, have high densities and melting points, and are solid at room temperature (except mercury, which is liquid).

What laboratory apparatus is shown, and what is its specific application in mixture separation?

A separating funnel; it is used to separate immiscible liquids of different densities (such as kerosene and water or cooking oil and water).

What separation technique is depicted, and what terms are given to the separated liquid and solid?

Filtration. The liquid that passes through the filter paper is the filtrate, and the undissolved solid left behind is the residue.

What is simple distillation, and what condition must miscible liquids meet to be separated by it?

Simple distillation is the process of vaporizing a liquid by boiling and re-condensing the vapor via a condenser. It separates miscible liquids that boil without decomposing and have a large difference between their boiling points.

What are the Latin names and standard symbols for sodium, potassium, iron, and silver?

Sodium: Natrium ($\text{Na}$) Potassium: Kalium ($\text{K}$) Iron: Ferrum ($\text{Fe}$) Silver: Argentum ($\text{Ag}$)

List seven elements that naturally exist as diatomic molecules.

Hydrogen ($\text{H}_2$), Nitrogen ($\text{N}_2$), Oxygen ($\text{O}_2$), Fluorine ($\text{F}_2$), Chlorine ($\text{Cl}_2$), Bromine ($\text{Br}_2$), and Iodine ($\text{I}_2$).

How is the chemical formula for the binary compound aluminum oxide determined using valence numbers?

Aluminum has a valence of $3$ ($\text{Al}^3$) and oxygen has a valence of $2$ ($\text{O}^2$). Criss-crossing their valence numbers gives the formula $\text{Al}_2\text{O}_3$.

What are four visible signs that indicate a chemical reaction has taken place?

1. Color change
2. Evolution of a gas (formation of bubbles)
3. Temperature change (exothermic or endothermic)
4. Formation of a precipitate (an insoluble solid)

What does the Law of Conservation of Mass state regarding a chemical reaction?

Matter is neither created nor destroyed during a chemical reaction; the total mass of the reactants is exactly equal to the total mass of the products.

What balanced chemical equation describes the industrial synthesis of ammonia?

$$3\text{H}_{2(g)} + \text{N}_{2(g)} \rightarrow 2\text{NH}_{3(g)}$$

How is the total magnification of a compound light microscope calculated?

By multiplying the magnification of the ocular (eyepiece) lens by the magnification of the objective lens (e.g., $10\times \times 40\times = 400\times$).

What are the three core principles of unified cell theory proposed by Schleiden and Schwann?

1. All living things are composed of one or more cells.
2. The cell is the basic structural and functional unit of life.
3. All new cells arise from pre-existing cells.

Which four structural components are shared by all cells?

1. Plasma (cell) membrane
2. Cytoplasm
3. Genetic material ($\text{DNA}$)
4. Ribosomes

What are three key structural differences between plant cells and animal cells?

Plant cells possess a rigid cellulose cell wall, chloroplasts for photosynthesis, and a large central vacuole, all of which are absent in animal cells (animal cells may have lysosomes and small temporary vacuoles).

What is the balanced equation for aerobic cellular respiration, and where does it occur?

$\text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 \rightarrow 6\text{CO}_2 + 6\text{H}_2\text{O} + 38\text{ ATP}$ It occurs in the mitochondria of cells.

What are the seven fundamental characteristics shared by all living organisms?

Movement, Respiration, Sensitivity, Growth, Reproduction, Excretion, and Nutrition (MRS GREN).

What are the seven hierarchical taxonomic ranks in biological classification from largest to smallest?

Kingdom, Phylum, Class, Order, Family, Genus, Species.

What are the five kingdoms of life in Whittaker's classification system?

1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi
4. Kingdom Plantae
5. Kingdom Animalia

What are the major structural differences between Bryophytes and Pteridophytes?

Bryophytes (mosses, liverworts) are non-vascular, lack true roots, stems, and leaves, and rely on moist environments; Pteridophytes (ferns) are vascular plants containing xylem and phloem, possessing underground stems (rhizomes) and true fronds that bear spores in sporophylls.

What is the true shape of the Earth?

An oblate spheroid (slightly flattened at the poles and bulging at the equator).

What are the precise equatorial and polar diameters of the Earth?

Equatorial diameter: $12{,}756\,\text{km}$ Polar diameter: $12{,}714\,\text{km}$

List the five vertical layers of Earth's atmosphere in order from the surface upward.

1. Troposphere
2. Stratosphere
3. Mesosphere
4. Thermosphere
5. Exosphere

What are the four primary interconnected spheres of the Earth system?

1. Geosphere (Lithosphere) - rocks and minerals
2. Hydrosphere - all liquid, solid, and gaseous water
3. Atmosphere - blanket of gases surrounding Earth
4. Biosphere - all living organisms

What are the primary physical consequences of Earth's rotation versus its revolution?

Earth's rotation (on its tilted axis every $24\,\text{hours}$) causes day and night, the deflection of winds/currents, and the rise and fall of daily tides. Earth's revolution (around the Sun every $365.24\,\text{days}$ with a $23.5^\circ$ axis tilt) causes the change of seasons.

What are the four main types of motion based on path followed?

1. Rectilinear motion: motion along a straight line.
2. Curvilinear motion: motion along a curved path (including circular motion).
3. Rotary motion: spinning on its own axis.
4. Oscillatory motion: to-and-fro or back-and-forth periodic motion.

What scientific instrument is used to measure force, and what is the standard unit of force?

A spring balance (Newton meter); force is measured in Newtons ($\text{N}$).

What are the major differences between renewable and non-renewable energy sources?

Renewable energy sources regenerate naturally, are nearly inexhaustible, and produce low emissions (e.g., solar, wind, hydro, geothermal, biomass). Non-renewable energy sources are finite, deplete over time, and take millions of years to form (e.g., coal, petroleum, natural gas, nuclear).

What are the 'Three Rs' of natural resource conservation?

Reduce (decreasing waste generation and energy consumption), Reuse (using products more than once), and Recycle (reprocessing used materials into new useful products).