Year 10 Chemistry - equations

Select the option that best completes the following sentence. All chemical reactions involve the conversion of:

• a solid substance into a liquid
• one or more chemicals into one or more new chemicals
• solids or liquids into gases

Identify the general form of all chemical equations.

• products → reactants
• acid + base → salt + water
• reactants → products
• metal + water → metal hydroxide + hydrogen

Carbon dioxide changes from a solid – dry ice – to a gas at -78.5°C. Determine what type of change this is.

• Chemical reaction
• Physical change

Select the option that best completes the following sentence. In a chemical reaction, atoms are rearranged by:

• some atoms disappearing, thereby breaking bonds
• the breaking and making of bonds
• new atoms being created and making new bonds
• simply mixing substances together

• 4 molecules of CH
• 4 atoms of carbon in a methane molecule
• 4 atoms of hydrogen in a methane molecule
• 4 atoms of methane

A molecule of carbon disulfide contains one carbon atom and two sulfur atoms. Determine the chemical formula.

Identify one advantage of symbol equations compared to word equations. Symbol equations:

• are difficult to understand, so keep chemical knowledge restricted to scientists
• show exactly which elements are involved and the relative number of atoms of each
• use plain English
• show both the reactants and products

Hydrogen chloride (HCl) can be formed by the following reaction: hydrogen + chlorine → hydrogen chloride Identify the symbol equation for this reaction.

Select the option that best completes the following sentence. The law of conservation of matter states that during any chemical reaction:

• a small amount of matter is converted into energy
• the number of atoms of each element remains the same
• the total number of atoms remains the same but some atoms may switch from one element to another
• the total number of molecules remains the same

Select the option that best completes the following sentence. Chemical equations are balanced by changing:

• the number of reactants and products
• the coefficients in front of the chemical formulas
• the subscripts in the chemical formulas
• the positions of the reactants and products