7B SCIENCE- chapter 6

What is the scientific definition of matter?

Anything that has mass and takes up space.

How is mass defined in science?

The quantity of matter in an object, usually measured in grams or kilograms.

Name the three common states of matter found on Earth.

Solid, liquid and gas.

Which state of matter has a fixed shape and a fixed volume?

A solid.

Which state of matter has a fixed volume but no fixed shape?

A liquid.

Which state of matter has no fixed shape or fixed volume?

A gas.

Which two states of matter are generally not compressible?

Solids and liquids.

Which state of matter can be compressed easily?

Gases.

What word describes the movement of one substance through another from high to low concentration?

Diffusion.

Why do gases diffuse faster than liquids?

Because gas particles move faster and are farther apart than liquid particles.

At what temperature does water melt (freeze) at sea level?

0 °C.

At what temperature does water boil (condense) at sea level?

100 °C.

What is the change of state from solid to liquid called?

Melting.

What is the change of state from liquid to solid called?

Freezing.

What is the change of state from liquid to gas at a substance’s boiling point called?

Boiling.

What is the change of state from liquid to gas below the boiling point, occurring only at the surface, called?

Evaporation.

What is the change of state from gas to liquid called?

Condensation.

What is the change of state from solid directly to gas called?

Sublimation.

What everyday substance is known as dry ice?

Solid carbon dioxide.

At roughly what temperature does dry ice sublime?

–78.5 °C.

Why can CO₂ be stored under high pressure in fire extinguishers?

Because gas particles are far apart and can be compressed into a small volume.

List the four main ideas of the particle model of matter.

1) All substances are made of tiny particles; 2) Particles in liquids and solids attract each other; 3) Particles are always moving; 4) The hotter the substance, the faster its particles move.

According to the particle model, what happens to particle motion as temperature increases?

Particle motion speeds up.

Why can most solids not be poured?

Their particles are locked in fixed positions by strong attractions.

How many cubic centimetres are equivalent to one millilitre?

1 cm³ equals 1 mL.

What simple technique is used to measure the volume of an irregular solid?

Water-displacement in a measuring cylinder.

Define precipitation in meteorology.

Falling water in solid or liquid form from the atmosphere.

List four common forms of precipitation.

Rain, hail, snow and sleet.

How do hailstones become large inside a storm cloud?

Updrafts carry frozen raindrops upward repeatedly, adding new ice layers each cycle until the stone is heavy enough to fall.

What does humidity measure?

The amount of water vapour in the air.

What is the name of the science that studies and forecasts the weather?

Meteorology.

Which device carries weather instruments high into the atmosphere?

A weather balloon.

Why are small gaps left between lengths of railway track?

To allow metal rails to expand on hot days without buckling.

What causes a bathroom mirror to fog after a hot shower?

Water vapour in the air cools on the cold glass and condenses into tiny droplets.

Why does a hot-air balloon rise?

Heated air inside expands, becomes less dense than surrounding air and provides lift.

What happens to gas pressure in a sealed container when the gas is heated?

Pressure increases because particles collide with the walls more often and with greater force.

In science, what is a ‘fluid’?

A substance that flows—namely liquids and gases.

Which state of matter generally expands the most when heated?

Gases.

When reading a measuring cylinder, how should you view the meniscus?

With your eye level at the bottom of the meniscus.

What unit is commonly used for small liquid medicine doses?

Millilitres (mL).

Why does water expand instead of contract when it freezes?

Its particles arrange into an open lattice that occupies about 10 % more volume than the liquid state.

Define volume in scientific terms.

The amount of space occupied by a substance.

What does compressibility mean?

The ability of a substance to have its volume reduced by pressure.

Clouds are made of what state of water?

Tiny droplets of liquid water suspended in air.

What is the practical difference between steam and invisible water vapour?

Both are water gas; visible ‘steam’ is water vapour that has condensed into tiny liquid droplets, while true water vapour is invisible.

Why does water boil at lower temperatures on mountain tops?

Because atmospheric pressure is lower at higher altitudes.

What is the SI base unit for measuring mass?

The kilogram.

During heating, what is the term for particles moving farther apart and the object getting larger?

Expansion.

What is contraction in terms of particle behaviour?

Particles slow down and move closer together, making the substance smaller.

During boiling, what happens to the temperature of the liquid until it is all converted to gas?

It remains constant at the boiling point.

Why is Pyrex glass preferred for cookware over ordinary soda glass?

Pyrex has a much lower thermal expansion, reducing the risk of cracking when heated.

What particle-level process lets cooking smells spread through a house?

Diffusion of gas particles through air.

1 L of liquid occupies how many cubic centimetres?

1000 cm³.

Why are overhead power lines hung loosely rather than tight?

To allow for contraction in cold weather without snapping the wires.

What is the direct change of state from gas to solid called?

Deposition (the reverse of sublimation).

How does increasing distance between particles affect their mutual attraction?

Attraction weakens as distance increases.

Define melting point.

The temperature at which a substance changes between solid and liquid states.

Define boiling point.

The temperature at which a substance changes between liquid and gas states.