science CAT test physical and chemical change

What are compounds?

Pure substances containing more than one different atom bonded together.

What is a physical change?

When a substance looks different but its particles have not changed

What is a chemical change?

When a new substance has been formed that has different particles then the original substance

What is evidence that a chemical change has taken place?

• a gas is produced

• there is a permanent change in colour

• light or heat is produced

• they are irreversible

• a solid is formed from 2 solutions

What is some evidence a physical change has taken place?

• changes to the objects shape

• is reversable

• phase changes like melting or freezing

What are some examples of a chemical change?

• burning wood

• rusting iron

• baking

• food going off

What are some examples of a physical change?

• melting ice

• boiling water

• chopping wood

• breaking glass

What is an endothermic reaction

Reactions that absorb energy energy from its surroundings causing them to become colder.

What is an example of an endothermic reaction?

• instant cold packs

• melting ice

• baking a cake

What is an exothermic reaction?

Reactions that release energy/ heat into its surroundings.

What is an example of an exothermic reaction?

• lighting a match

• explosions

• magnesium reacting with oxygen

What is an element?

Substances with atoms of the same element bonded together.

Is this an element or compound?

element

Is this an element or compund?

element

Is this an element or compund?

compound

Is this an element or compound?

compound

What is a chemical formula?

Something that scientists use to show types and numbers of atoms that make up a compound.

What are the different types of compounds?

• Ionic

• Covalent

What is an ionic compound?

Something that has a metal bonded to a different non metal

Give an example of an Ionic compounds

• Carbon oxide

• Sodium chloride

What in a covalent compound?

Something that has a non-metal bonded to a different non-metal

Give an example of a covalent compound

• water

• carbon dioxide

What are the rules for naming chemical compounds?

1. The ending of the final element is changed to -ide

What are the rules for naming ionic compounds?

1. write the name of the metal

2. write the name of the non-metal second and change ending to -ide

How do you name covalent compounds?

1. Write elements in the order they appear

2. A prefix goes in front of each element

3. If there is one atom of the first element no prefix is needed

4. The ending of the last element is changed to -ide

What is the prefix for one?

mono

What is the prefix for two?

di

What is the prefix for three?

tri

What is the prefix for four?

tetra

What are chemical changes also called?

Chemical reactions

What are products?

The new substance formed

What are reactants?

The original substance

Where do the reactants go in a word equation?

First

Where do products go in word equations?

second

How do you seperate the reactant and product in a word equation?

an arrow (→)

What is a synthesis reaction?

When two reactants combine to form one product

What is a decomposition reaction?

When one reactant breaks down into two products

What is a displacement reaction?

When one element in substituted for another

How do you represent Endo and Exo reactions in word equations?

By adding the word ‘energy’ to either the reactants or products

How do you know what side the energy should go on in a word equation?

• If energy is absorbed → reactants side

• If energy is released → products side